1. Field of the Invention
The present invention relates to imaging apparatuses, and in particular, to an imaging apparatus suitable for correcting image blurring caused by shaking of the imaging apparatus.
2. Description of the Related Art
When an image is captured by a camera, camera shake may cause image deterioration. To prevent this image deterioration, an image-blur correcting device for optically correcting image blurring has been developed.
The image-blur correcting device includes a shake detecting sensor having an angular velocity sensor for detecting camera shake, a correction calculation unit including an integrator for converting information detected by the sensor into a signal representing a driving position (target position) of a correcting lens, and a lens driving unit including a driving circuit and an actuator for driving the correcting lens.
A vibrating gyro sensor or the like is used as the angular velocity sensor. By integrating an output signal sent as velocity information from the gyro sensor, the output signal can be converted into positional information. By controlling the correcting lens to track the position represented by the positional information, an image-blur correcting operation is realized.
When a single-chip microcomputer separate from other functions serves as a device for performing operations such as integral calculation and on-and-off management of an image-blur correcting operation (anti-shake operation), in many cases that microcomputer consumes a current of 20 milliamperes or greater. When a detection circuit and a driving circuit operate, a current of several tens of milliamperes or greater is consumed as a circuit consumption current.
In portable products, such as digital cameras, it is common that batteries are used, such as lithium-ion batteries or nickel-cadmium batteries. When a product uses a power supply having limited power, such as a battery, consumption of unnecessary power prevents the product from being used for a long time.
To solve the above problems, two types of imaging apparatuses of the related art are known. In one type (e.g., Japanese Patent Laid-Open No. 7-294982, corresponding U.S. Pat. No. 5,701,521), after completing an image capturing operation, a microcomputer is switched to a low power consumption mode. In the other type (e.g., Japanese Patent Laid-Open No. 2001-169176), a controller is changed in response to a playback operation.
In the case of stopping an anti-shake operation when switching the image capturing mode to a playback mode for displaying the captured image data, a certain amount of time is required until the next anti-shake operation is performed. This required time includes the time required for a camera-shake-detecting angular sensor to become stabilized, the convergence time required for arithmetic operations for control, and a reset operation time for the correcting lens.
When a desired scene, whose image is to be captured, appears for only a short time after switching the image capturing mode to the playback mode, the playback mode must be switched to the image capturing mode again for image capturing. However, in a case where the anti-shake operation is immediately stopped on switching to the playback mode, as in the related art, when the playback mode is switched to the image capturing mode just after that, the image-blur correcting device cannot be immediately operated, so that a certain amount of time is required, as described above. In this case, image capturing with the anti-shake operation activated is not possible, thus causing the possibility of losing a photographing opportunity.
In addition, when image capturing is performed before the above time elapses, the captured image may have image deterioration since image blurring occurs due to the fact that image blurring is not corrected.